A medical adhesive sheet used by adhering to a skin surface is used for various uses as a medical adhesive sheet for covering to protect skin surfaces, a medical preparation for percutaneously admistrating a drug into a body. However, since the surface to be adhered is a skin surface, at the development thereof, the handling property at adhering, the follow-up property (flexibility) to the movement of the skin surface, non-irritative property to the skin, etc., are important required characteristics. Also, in a medical preparation, the characteristics such as the impermeability of a drug from the back surface of the support, a drug releasing property, etc., are required. In particular, such a medical adhesive sheet is sometimes in an adhered state for a relatively long period of time and in such a case, the medical adhesive sheet showing no feeling of discomfort after adhering to the skin surface and giving no irritativeness to the skin is considered to have important required characteristics.
For meeting such requirements, a medical adhesive sheet wherein the thickness of the support is reduced as thin as possible, whereby the irritativeness by the edge portions of the support is reduced and further the skin follow-up property is imparted has been proposed. However, when the thickness of the support is thinned, although the above required characteristics can be satisfied, the medical adhesive sheet itself loses the self-supporting property, causing the problems that the handling property at adhering is reduced, after adhering, the medical adhesive sheet creases and also the adhering surfaces adhere to each other at adhering, whereby the medical adhesive sheet cannot be finely adhered.
Thus, to overcome the above problems, a medical adhesive sheet wherein a pasteboard having a self-supporting property is temporarily bonded to the back surface of a support film having a thin thickness and a medical adhesive sheet wherein a material having a flexibility, such as a polyurethane film, etc., is used as the material for the support itself and the thickness of the support is increased to some extent to improve the handling property have been proposed.
The former medical adhesive sheet is described in JP-A-55-32553, JP-A-64-16719 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-A-U-56-57235, JP-A-U-56-158215 (the term "JP-A-U" as used herein means an "unexamined published Japanese utility model application"), etc., and is excellent in operability at adhering. However, in the medical adhesive sheet, if the control of the adhesive force at temporarily bonding the self-supporting pasteboard is insufficient, it sometimes happens that the pasteboard is released before adhering the medical adhesive sheet and also in separating the pasteboard after adhering, the medical adhesive sheet itself is also separated. Thus, it is necessary that the adhesive force for temporary adhering is controlled with a sufficient care. Also, in this case, since the surface of the support film is relatively smooth, the adhesive force (anchoring force) to a pressure-sensitive adhesive layer becomes sometimes weak, and as a result, when the medical adhesive sheet is separated from the skin surface, there is a possibility of causing a so-called adhesive remaining phenomenon that the pressure-sensitive adhesive remains on the skin surface.
On the other hand, in the latter medical adhesive sheet, although the material for the support is a soft material, since the thickness of the support is increased, it sometimes happens that in the case of adhering the medical adhesive sheet for a long period of time, the irritativeness by the edge portions of the support cannot be sufficiently reduced.
In particular, in a medical preparation containing a drug which is percutaneously absorbed into the body by strictly controlling the doses of the drug, the improvement of the handling property and the reduction of the skin irritativeness described above are important problems to be overcome and the development of the technique which can overcome these problems has been actually desired.